Tunneling.



J. F. OROURKE.

TUNNELING. vlumlcnmou FILED ria. l. |919,

Patented Aug. 27, 1918"- l SHEETS-SHEET 2 0%? www we.

@MW n @55M J. FOROURKE. TUNNELING. A'Pmcfnou hun ria. l'. ma.

'Patented Aus. 21, 19m l igt J. F. GROURKE.

TUNNELmm APPLICATION FILED FEB. 1.1918.

E SHEETS-SHEET 4.

@www "Af-@M I. F. O'ROURKE.

TUNNEUNG. y

APPLICATION FILED FEB. I IQIB.

1,277,1@1 Patented Aug. 27, 191s.

6 SHEETS-SHEEI' 5.

J. F. URUUHKE.

TUNNELING. APPLICATION FILED FEB. l. 19,18.

'Patented Aug 27,1918

wwf a Jolmwowourk UNITED STATES PATENT OFFICE.l

JOEIN F. OROULILKLEI,r OF NEW YORK, N. Y.

TUNNELING.

Specification of Letters Patent. Patente Aug', .27, 191 8.

Application filed February 1, 1918. Serial No. 214,877.

To all whom t may concern:

Be it known that I, JOHN F. ORoUuxa,

face would not stand up of itself and into such spare the shield wasshoved forward thus providing space in the tail of the shield in whichto erect another ring.l Repeating this process of excavation, shovingand erecting successive rings constitutes the method of shieldtunneling.- y

As the bottom of the shield is usually'. built about the length of aring or shove shorter than the top, .the faceJof the excavatio'n liesjust under the end of theshield at the-top, and a slope of earth isallowed to stand at the bottom when the ground per'- mits, into whichthe shield readily. shoves,

so that generally the vertical face of the excavation extends onl 1mm.In 'soa grou ,like sin, the shield is closed in front and shovestheground ahead of it, or the shield may have a small opening throughwhich some of the ground enters during a shove, but this condition isunimportant in designing the shield as it must be prepared to go throughharder ground when encountered, and so is valways built with an openface overhanging at the top.

`It is also usual to divide the shield into two or three levels at theforward end` divided by platforms fitted with extensible fronts operatedlwith hydraulic jacks from which the `excavation is carried on, andwhich hold the timbering and breast boards before and during the shove.These platforms have always been designed to reach the one verticalyface heretofore used and "the form of the Vshield itself'hasbeen'adapted to inclose one vertical faceof the excavation.

When a tunnel is under water or in waterbearin'g ground compressed airis generally used. The pressure is usually maintained in the tunnel andshield alike, equal to the pressure in theground water at or near theonly part way to the bot-' bottom of the shield, so that the pressure 0fthe compressed air at the top of the shield is in excess of the pressureof the ground water at that level, proportional to the height of theshield. The tendency of this unbalanced pressure is to blow out theground at the top of the shield, which sometimes happens When the coverof earth is insuilicient to hold the air. The usual practice to preventthis is to maintain.. a cover vof earth one and a quarter times thediameter of the tunnel above the shield, which A gives a small margin ofweight in excess of l the lifting power of the unbalanced air pressure.

It is obvious that if the air pressure 'at the top of the shield couldbe'kept atsomething near the water. pressure at that i, oint that` thedanger of blowouts would e greatly lessened, and that the work would bedone 1n the upper part of the shield underless air ressure and with lessand abor. of the larger tunnels-that have'been constructed, and in theshields for which airA chambers on separate levels wereiprovided, but itwas 4foun impossible', in the desi gn of shlelds used, to preventthehigher ressure in the lower air chamber from passing into` thatabove4 at the common vertical face.

As the tunnels in which the attempt was made, so far as I am aware, wereof mqd'- erate diameter and well within the limite` up to'which clayblankets could be used v(if suficient thickness to counter-balance theunbalanced air pressure, the work was done Without the use ol themultiple air pressures. Had a tunnel been designed of such size thattheclay blankets would block up the river above, such tunnels would nothave been built by the known methods and a number of smaller tunnelswould have been built, wherefore small tunnels have been thenruleheretofore. i

One object of my invention` is .to rovide meansby which air chambers intie forward part of the shield on successive levels can maintain airpressures in each suitable for 'working against the water pressure inthe ground ,in mnt of itself without being aifected by the higher airpressure of a lower cost for" power This Vfatt was perceivedlu some tionin eorres|mmliug steps, separated from ear-h other by floors in theshield. and their cutting edges on the forward parts, thereof, which areair tight and compel the comt5 pressed air that escapes into the groundto ascend without obtainiugacress to the chamber above. lintrauce of airfrom a chamber below into a chamber above is etfectually prevented b vthe tact that'. thi` compressed air when it enters the ground andcommences to rise. immediately expands to the pressure of the adjacentground water, which pressure is constantly lasst-ning upward. so thatthe es( apingr an' in the ground can liever be at a higher pressure thanthat ot' the air in the chamber itlis passing, since that pressure alsois regulated by the water pressure in front.

There might be circumstances in which it would be advantageous to havethe air chambers step backward from top to bottom and also cases inwhich the air chambers would be given independent telescopic motion inthe shield` but the principle remains the same of maintainin the. facesof the excavation in Ldifferent mrtlcal planes so as to' spillseparately theV compressed air o fditferent pres- -su'res'f-out intothe'groundwhere Vthey can harmlssly expand unconfned'.

The height of the 4floors above one another can be' made as mostconvenient -for theexcavation and unbalanced air ir'ess'ure. The

, unbalanced air pressure iat t ie top of the shield-in thecase ofmultiple air chambers necessary earth cover, or clay blanket in lieu ofsame, is no longerrequired proportional tthediarneter-'ofthe #shieldbutto `the heightof the top air chamber where that or chambers bclow andso with my improved shield the formel-'limitation of size of tunnels tobe constructed with the use of. compressed air disappears.- 1

plished by having air chambers ea able of maintaining di'erent pressuresat i'erent levels is that the pressure in the tunnel itself can'bemaintained at a desired pressure independent et the air pressures in theair chambers. The d'oorsof the air locks are hung` on the sides of theopenings inst which the pressure comes. The air loc S are fitted ,withbutts inside and outside of the openings so that when the doors are huncorrespondingly they act. equally we whether the 'higher pressure is inthe air chamber or in the tunnel. The aforesaid independence ofpressures between those at the front. of the shield and that in thetunnel proper gives great latitude in the use of compressed air intunnel construction. Heretofore if the top of tite. shield was abovewater level in loose ground with enough wa' G5 ter in the ground at thebottom part of the isonly that of the top chamber, so'that the'height-is not less than that of the chamber- Another very importantobject accom-- shield to require the use of compressed air, greatditiieulty was encountered because of the water, even in small diametertunnels. By the use of my improved shield, having air chambers adaptedfor different pressures corresponding to the water pressures at theirfronts, the aforesaid ditiiculties are overcome. Air chambers above thewater level would contain free air. Such free air chambers and anychambers below water level holding compressed air of less pressure thanthat in thetunnel, would have their air locks arranged to hold againstthe tunnel pressure and thus former ditiiculties in holding compressedair in'a tunnel that is partly above water level is obviated. Theimportance of the foregoing is obvious when it is considered thatimproved methods of shield tunneling enable such tunnels to be drivenunder city streets without disturbing the surface or adjoining buildingsand that by reason of this improved shield'the matter of where the topof the ground water lies is no longer of importance, since compressedair can 'be used with the to i of the. water lyilplg at any level in theshie d,-;f

invention alsocoinpriscs' no vel details of nnprove'menLand combinationsof arts that willwbe more fully hereinafter set orth and thenpointed'outJnthe claims.

Reference is to lbeliadto theyaccompanying drawings forming art hereof-whereim g `ig'ure 1 is al'vc'rtrca sectionof-a-tunnl shield embodyingmy invention,lillu'strating the location of the sheetingorbreastboarding 1 00 l at the'face oiseveral. com artments beforeshoving the ShieldfprWar ly; '-'Figs. 1 and l" are detail` sections'throughjair locks in the shield; Fig. 2 iszayiew 'substantially similarto Fig. 1, illustratin the shield as shoved forwardly iii thefearti,'ffshowing the faces of several working lair-chambers on di'erentplanes ready 'for excavation thereof; Fig. 3 is an enlarged detailsection of the cutting edge of a chamber of the shield; Fig. 4 is an endview of the shield looking from the'lefthand side of Figs. 1 and 2; Fi 5is a cross section of an air lock of the lshield; Fig. 6 isa perspectiveview within a tunnel lookin in the direction of my im- 1 15 provedshield, iustrating astep in the erection ofblocks in the tunnel lining;Fig. 7 is a vertical section of my-im roved shield provided with movabler'orklng air chambers; Fig. 8 is an enlar ed detail of part o f Fig. 1207 ;-Fig. 9 is an en urged section illustrating movable working airchambers of the shield; Fig. 10 is an enlarged detail of part of Fig. 9.

n the accompan ing drawin the 'numeral 1 indicates t egnor s ell of the125 main body )ortion ofl l improved shield` which may e constructed inany approved manner, such as by means of plates, beams and the likeproperly riveted and bolted together as usual in a circular form of tun-18.0

' nel shield. Within thtail of the shield the rings 2 of the tunnel ningmay be erected in any usual or suitable manner, wluch'rings may compriseblocks 21 of concrete, metal, or other material installed in any desiredmanner. Within the shield, and forward of the tail portion where thelining is erected, are working air chambers indicated at 3,11, 5, (i,which are open at their forward or cutting edges, which forward orcutting edges are on different planes` and said chainbers are ondifferent levels. There may be two or more such chambers on differentlevels according to the diameter of the shield or the work to be done. Ihaveillustrated chambers on four levels assuming that the shieldillustrated is adapted for the construction of a tunnel of relativelylar e diameter, sayr from forty to fifty feet in iameter. The floor orbottom Wall 7 of the Y lowest chamber and the roof or upper wall 8 ofthe upper chamber may be comprised in the wall or skin of the shield,and the Hoors of the intermediate chambers may comprise platforms 9` 10and 11 suitably built horizontally within the shield. Such floors orplatforms may comprise horizontally disposed beams 12 and upper andlower plates 13, 14, preferably riveted together and secured to the skinof the shield, whereby the floors or platforms wi ll be united to theskin of the shield in a rigid and lair Itight manner. A partition orwall is indicated at l5 at the rear of each chamber, and which may besecured to beams 16 that are'secured 1between the several -floors. Angleirons at "1 7fmay be provided between the floors, walls 1,5-and beams 16for rigidly securing them together and to make air tight joints. At 18are air locks for each chamber adapted to open at one end within thecorresponding chamber and at the other end within or toward the tail ofthe shield behind thewall 15. Said air locks may be of any approved form`-secured air tight in openings in the Walls 15, as by means of angleirons 20 riveted respectively to thcwall l5 and posts 16. Doors 21, 22are provided at opposite ends of said airlocks to permit the passage ofmen and materials to or through the air locks. Since there will be,under some conditions of use of 'my improved shield,

material difference of air pressure in thelocks, on the lefthand sidesfacing the locks from either end, (Figs. 1, 1", 2, 4; and 5), and thebutts 25 are on the inside faces of thel end walls of the air locks, buton the opposite sides of said end walls with respect` a chamber 3, 4, 5or 6 is greater than that in the tunnel, the doors may be hung agalnsttheends of the air locks, as illustrated in Figs. 1 and 2, wherein thedoor 22 within the chan'ibcr closes against the exterior of the end wallof the lock within such chamber` and the door 21 within such lock closesagainst the inner wall at the rear ot' the lock toward the tail of theshield, whereby passage through such lock under such different airpressures may be effected. If, however, the air )ressure within one ofsuch chambers is equal to or lower than the air pressure within thetunnel such doors will be re` versed, that is to say, the door 22 wouldbe removed and replaced within the lock and hung upon its forward buttstherein to swing against the wall of the lock `within the chamber,.andthe. door 21 wouldbe removed and hung upon the butts 25 within the tailof the shield, to swing against the exterior face of the wall at therear of such loclft` within thel tail of the shield, whereby passagethrough the lock may be effected. The arrangement described is such thatonly one door is provided for each end of each lock, and by reason ofthe ability to shift the door so as to swing against the outer or theinner face of an end wall of the lock, there is no danger of improperlysetting the doors at the ends of the lock with respect to air pressures,which might occur were two doors provided at each end of the lock, suchas one exterior thereof and one therein.

With the' arrangements described, air pressures may be, maintainedwithin the chambers 3, 4,- 5, 6 of any desired degree irrespective ofthe air pressure i'naintained within the tail of the shield beyond thelocks and within the tunnel, to hold back water and ground `at-'tllefaces 2G in the cxcavations in the earth. The forward working or cuttingedges of the chambers 3. 4, 5, 6, indicated at 3, 4*, 5, 6, are indifferent planes and different levels, which is effected by having suchcutting edge of one chamber extending forwardly beyond the maincircumferential portion of the shield farther than lthe cutting edge ofanother chamber.' In the accompanying drawings I have illustrated thecutting edge of chamber 2 as ex'- tending farther forwardly than thecutting edge of the chambers thereabove, the cutting edge 4' asextending farther forwardly than the cutting edges, 5*. 6*, and thecutting edge 5 as extending farther forwardly than the cutting edge'ti.Such arrangement will hold good with respect to the number of 3 suchcompressed air working chambers as the shield may be provided with,whereby the chambers and their respective cutting edges extend beyondone another in steps. By the arrangement described a higher air l0pressure may be maintained in a lower chamber than in a chamber orchambers thereabove, and so on with respect to each of the chambersupwardly. The aforesaid cutting edges may bc constructed in any suitablemanner, such as by means' of Ysections securely fastened respectively tothe skin and to the walls or platforms 9, l0, 1l of the shield, asillustrated in Figs. 1` 2 and 4. Since the shield is circular in form.

the lower cutting edge 3b of chamber 3 and the upper cuttin edge 6 ofchamber t) are attachedto the s in of the shield, (the cuttin edges 3*,4, 5' being respectively attac ed to the'floors or platforms 9. 10. ll,:is

g5 above stated), and the cutting edges 4", Ji"

at the sides of the chambers Pand '5 re-. spectively are attached tothe' corresponding portions of the skin of the shield (sec Fig. 4).'

Within each working chamber 3,4. 5, 6 suitable supports'27 and abutments28 :ire secured adapted respectively to support and `oppose suitablejacks 29, whose plungers or ram`s 30 are ada ted to coperate with suit-85 able' breastlboartlling or sheeting and rangers 31, 32. )lacedagainst the corresponding faces26 o the several excavations totemrporarily retain such sheeting in a well nown manner.. Said jaeksmaybe hy- 40 draulie jacks 4'controlled in the usual way, (Fig. 2). At 33are jacks tted within the tail of the shield to coperate therewith andwith the tunnel lining rings 2, for shoving the shield forwardly, in anywell known manner. I The jacks 33 may be hydraulic jacks operated in ausual n'ianner for shoving tunnel shields. I

While I have illustrated and described a shield constructed with theworking charnbers 3, 4, 5, 6 arranged on different levels, with suchchambers projecting respectively farther outwardly from the bottom tothe top, somewhat in the nature of a flight of steps, it will beunderstood that the principle of my invention may be carried out inconjunction with a shield 1n which the an' chambers projectfartheroutwardly from the top downwardly than from the bottom upwardly, that isto say, that the upper cutting edge of an upper chamber projects'fartheil outwardly than the upper cutting edge of another chamber orchambers therebelow, and so on correspondingly downwardly, so that thecutting edge of a lower chamber willproject less outwardly than thecutting edge of a chamber or chambers thereabove, as like Steps leadingbackwardly. ISuch :form of shield might be used for tunneling Nhe'resand is at the top and clay at, the bottom, and the diffusion of the airwithin the ground will be such -as to overcome the. mingling of air 0f ahigher pressure from a chamber on a lower level with air of n. lowerpressure in a chamber on a higher level, since the faces 26 of theexcavations 75 on the different levels are in different planes andconsiderable earth intcrvenes between the cutting edge of one chamberand the cutting edge of another chamber.A i

)Vliilc 1 have described a tunnel shield 80 wherein the working airchan'ibers 3, 4, 5, (iare fixed in relation to the main body of theshield and work together 'as a unit, it will be understood that myimprovements also contennilate a shield wherein the air chambers haveindependent movement with respect to the shield and to one another. Sucha construction is illustrated in Figs. 7 to 10. In such constructioneach of said chambers muy be made with all of its walls separate 90 fromthe parts of the shield. the rear wall 15 ofeaeh such chamber beingsecured tb to, bottom and side walls 15'1 thereof, rigidi) connectedtogether in any suitable manner, such as by posts 164'. The cuttingedges '3"l 95 'tom vwalls of said chambers rest; iipon,'the

floors. or platforms 7, 9, 10 and 11.2 'Ehere'ar portions of the cuttingedges 3*, 4'i, 5*, 6?, are shown provided with webs 3, 4f, 5u, 63,'respectively overlying or opposing adjaeparts of the floors 9, 10. 11and the skid 8 of the shield, the cutting odge 3* having a web 3opposing the skin at the lower part of the shield (Fig. 7). The interiorof each 110 of said movable working chambers may be provided withuprights or abutments to eooperate with the jacks 2t) in ii 'mannerbefore described. Jacks 35 (such as liydiauliev jacks before referredto) may be secured td i-l5 each movable chamber 3, l, 5, 6 in positionforcoperation of its plunger or' ram 36, with an abutment 37, such asa'n I-beam, sc-' cu'red within the shield behind the corre,

s ending movable chamber (Figs. 7. 8 and 120 9g, whereby said chambersmay be moved forward toward the face of the excavation as required. Thejacks 35 of each chamber may be located in a jack circle indicated ai:

18 which may comprise plates 18b and posts 125 18 secured between thecorresponding air lock 1S and wall 15 of a workingr chamber,

to prevent- .passage of air around the. locks between the. tunnel andthe chambers (Figs.

7 and 8). With the arrangement described, 180

the desired air pressure may be maintained in each of said movableworking chambers as in manner before set forth, and when the excavationsat the open ends of such chambers have been completed for each step andthe sheeting applied and sustained by the jacks 29, the jacks 35 of thecorresponding movable `working chambers may he operated to. force 'suchchambers forward in proper .10 orderV to the required extent inaccordance with the excavation made 4in front thereof, each cliam'berthere\1pon sliding forwardly within the shield. When such movements of`said chambers have been completed, thc en tire s'hield may be movedforwardly byv the operation of v,the jacks 33, the jacks 29 and 35 thenbeing relieved of pressure as required while the shield moves forwardlyalong the chambers 3, 4, 5, 6 to a required position, and the work ofexcavating in front of said chambers may again proceed, and so on. Bymeans ofthe movable working air chatnbcrsv'withi the shield it will beapparent that `all of the advantages before described may be carriedout, and also that one of the movable chambers may be moved forwardlymore or less for any given shove ofthe main body of the shield in caserock or other obstruction may have been encountered in front -of suchchamber which slowed the V work as compared to the work done in front ofthe otherchamber or chambers at any given time. r

By `means ofthe arrangements described,

' a5 a plurality of faces or working points of the tunnel excavation arerovided independent of one another, on di erent planes, and the 'heightof each working face is less than the lvertical diameter of the shield.While, 40 undersome circumstances, the air pressure in all of thechambers may be the same, and if.desired, the same as within the tall ofthe shield andthe tunnel, a great advantage o f my'impro'vement is thatthe air pressure in one working chamber of the shield may be less thanthe air pressure in one or more other of'such chambers, such asaccording to the diameter of the shield-and the depth in the earth atwhich the tunneling is carried on; 1n other words,l compressed air maybe used of suitable-pressure for the level at which any of the chambersis located, vand. not as customary in shielddriven tunnels at a comnionressure for the whole shield and tunnel, an the air pressure in onechamber will be maintained se arate from the air A ressure'in the otherc amber or chambers, by reason of the. fact that the face 26 of theexcavation 4of a lower chamber projects far- A ther into the round thanthe face 26 of the excavation o any chamber or'l chambert thereabove,since the air under a higher pressure escapes from a lower chamber mbo4the ground in front in a lane different from the plane of the face oraces 26 thereabove.

As such air rises nnconfined from a given working chamber of the shieldit continually expands to the same pressure as' the ground water at thelevel it 1s at the moment pass. ing, and since each air chamber 3, 4, 5,6 70 may have its compressed air regulated to suit`the water pressure inthe ground at its front, it is apparent that such air will. not enter anupper chamber or affect its air pressure, since the pressure of the airescaping from a lower chamber never exceeds the pressure in the groundwater holding'it. \Vhle different mr pressures have heretofore beensuggested for tunnel shields, it was, so far as I am aware, only inconnection with a shield having one common working face for excavationin the earth, hence the air pressure can pass from a chamber on onelevel to a chamber on another level to affect or raise the air pressurein the lat.- ter without the outside or independent diffusion in theound of the air from the chambers,l whic my invention provides for. Thework of excavation, applying the sheeting or breast-boarding andsustainin them with the jacks 29 may be carried on 1n each, workingchamber of the shield under a given pressure,.without-regard to the airress'ure 1n any other cha'mber, 'whereb w en 'the faces 26 at thedifferent levels o the excaya- 95 tion have all been completed to therequired position'for each chamber, the entire shield may be shovedforward a suitable. distance so that similar work for the ,faces at theseveral levels may continue 'preparatory tn another shove of the shield,and so on successively, It will be noted that during the excavation ofaface 26 ofa lower chamber of the shield, the earth above theforwardportion of such chamber, into which the face 105 26 of the excavation ofthe chamber next above is'being made, is sustained .intact by theforwardly rejecting upper portion of the lower cham er, and so on forthe chainbers on each level, such earth above 'such 110 forwardlyprojecting portion of a. lower chamber thereby acting as an obstructionagainst the flow of com ressed air from`a chamber below into anot erchamber above.

Another important feature of my in\'en- 115 tion is that in cases wherethe top of the shield is situated only a short distance below the waterlevel, or even above the water level, one or more working chambers mayhave the doors of their air locks arranged to hold against a higher airpressure in the tunnel than in `a working. chamber, whereby a tunnel maybe driven with water in front of the shield in its'lower vpartheld bycomres'sed air in its lower working air cham- 125 ers, with the tunnelitself containing compressed air which is prevented from escaping at thetop by means of the upper air chamber or chambers either heldin air oflower pressure than that in the tunn or even free air when such chamberis above the water level. A further important feature of my invention isthat the use of compressed air may be restricted to the working chambersof the shield. leaving free air in the tunnel.

An advantage of in v invention is that since a lower airlplessure may bemaintained in an upper chamber than in a lower chamher, a great savingin the cost of operation may be etl'ected. because of the less cost ofmaintaining such air pressure and because wages of the workmen are lessunder low air pressure than under high air pressure, and they can worklonger per day under low air pressure than under high air pressure, andwith less danger.

lVhile l have illustrated the shield and liningr rings of circular form,the. latter constituting a circular cylinder, it will be understood thata cylinder of any other form may be constructed by the method andapparatus set forth herein` the form of the cross section not being anessential part of my invention.

Having now described my invention what I claim is: y

1. The method of constructing a shield driven tunnel consisting inexcavating the ground at the front of a shield in separate chambers` ondifferent levels and producing faces of the excavations in steppedrelation in front of the several chambers, advancing the shield towardsuch faces, and erecting a linin within the tail of the shield aftersuch a vances.

' 2. The'mcthod of constructing a shield driven tunnel consisting inexcavating the earth in front of a shield in separate chambers ondifferent levels and producing faces Qf the excavations at the front ofsuch chamliers in different upward planes, maintaining air pressuregreater in a lower than in an upper chamber to restrain the flow ofwater and material from said faces, advancing the shield toward saidfaces, and erecting a lining within the tail of the shield after suchadvances.

3. The method of constructing a shield driven tunnel consisting inexcavating lthe earth in front of a shield in separate chambers on dili'crent levels in which a chamber on one level is longer in thedirection of the tunnel than a chamber on another level, producin rfaces of the excavations in the front of suc 1 chambers in differentplanes forward of one` another, maintaining air pressure ater in a lowerthan in an upper chamr, advancing the shield bodily?, toward said faces,and erecting lining within the tail of the shield after such advances.

4. A shield for tunneling having separate chambers at its forward end ina unitary structure, the forward end of one chamber extendin fartheroutwardly than the f0rward en of another chamber.

5. A shield for tunneling having a plurality of workin chambers in aunitary structure at its orward end on different levels, one chamberhaving a cutting ed located farther forward from the main bog; of theshield than the cutting edge of another chamber.

(l. A shield for tunneling having separate chambers in its forward parthaving-their forward edges extending beyond another in stepped relation,and an air lock for each chamber, said locks all being adapted tocommunicate with the space within the tail of the shield.

7. A shield for tunneling having a plurality of horizontal floorstherein and transverse walls between the floors providing a plurality ofchambers at the forward part of the shield, one floor extendin fartherforwardly than another floor, and cutting edges at the forward ends ofsaid floors located in different vertical planes.

8. A shield for tunneling having a plurality of horizontal floorstherein, beams se.- sured between said floors, transverse walls securedto said beams and to the skin of the shield providing chambers ondifferent levels within the shield, a chamber onone level extendingforwardly from the main body of the shield farther than a chamber onanother level, and air locks in said walls.

9. A shield for tunneling having unitary chambers in its forward partextending beyond one another in horizontal stepped relation, jacks intiers and upright suplmrtstherefor at the forward end of each chamberwhereh v the jacks in each chamber may hold sheeting at the face of theexcavation in cach chamber.

10. Apparatus for shield driven tunnels comprising 'a shield havingunitary air chambers in different levels and different face planes instepped relation, and means for maintaining air pressure in one chamberindependently of the pressure. in anyv other chamber.

Signed at New York city, in the county of New York and State of NewYork, this 29th day of January, A. D. 1918.

.ioHN F. oRoURKE.-

